High temperature alloy



Oct. 19, 1965 A. H. FREEDMAN HIGH TEMPERATURE ALLOY Filed Oct. 3. 1961 DOQ OmN-

OOD-

Gmb.

OOON

OnNN

OOmN

INVENTOR. A//an H. F eed an ffm i.

H/s ATTORNEY United States Patent O 3,212,886 HIGH TEMPERATURE ALLOY Allan H. Freedman, Inglewood, Calif., assignor to Armco Steel Corporation, Middletown, Ohio, a corporation of Ohio Filed Oct. 3, 1961, Ser. No. 142,726 5 Claims. (Cl. 75-171) My invention broadly relates to nickel-base alloys and particularly concerns both the alloys and various products formed therefrom, all possessing superior high temperature properties.

An object of my invention is to provide a nickel-base alloy, the essential alloying elements -of which are readily available and are present in the alloy in such proportions as to be economically feasible; which alloy is readily produced in the conventional electric arc furnace in substantial tonnage; and which alloy lends itself to a var1ety of working and forming operations, to welding by the electric arc or other techniques, and to age-hardening to achieve a maximum strength.

A further object is to provide a nickel-base alloy which readily lends itself to various applications in the form of castings, forgings and the like, while displaying advantageous high temperature characteristics, notably high mechanical strength, good stress-rupture properties, resistance to creep, and good scaling resistance, even in the presence of strongly oxidizing atmospheres, all at temperatures ranging upwards of 2200 F.; and which alloy, as well, displays adequate strength at room temperature.

Another object is to provide a variety of articles and products produced from an essentially nickel-base alloy of the general type described, widely varying in dimensions, mass, configuration, surface, mode of treatment both in manufacture and in service, and in application, all having in common a highly satisfactory response to arduous duty both at room temperatures and at prevailing high temperatures, under demanding and severe atmospheric conditions.

Other objects of my invention in part will be apparent, and in part pointed to in the description which follows.

Accordingly, my invention resides in the composition of ingredients, in the range and proportion thereof, and in the relation of each of the same to and with one or more of the others, as well as in the various articles and the products fashioned thereof, the scope of which invention is more fully set forth in the claims at the end of this specification.

The stress-rupture properties of the instant alloy as compared to those of a number of commercial alloys of the prior art of like application are graphically illustrated in the single figure of the accompanying drawing.

As conducive to a more ready understanding of my invention, it may be noted at this point in the disclosure that much attention has been directed to the problem of dividing metals for high temperature service. Such demand has become emphasized in recent years, and this in widely varying fields of application. Typical of these are the usual auxiliaries encountered in heat-treatment furnace practice. Thus, annealing furnaces require stools, separator plates, -base plates and the like, all serving to support the products undergoing anneal. Almost uniformly, these -components heretofore have had but a limited life, a phenomenon readily understandable in view of the temperatures encountered. Base plates, for example, are subjected on their bottom faces to temperatures above 2200 F. `The separator plates and the stools commonly are maintained at about 2200 F.

Aircraft and missiles are elds of application demanding metals capable of reliably withstanding high temperature exposure. Turbine blades give rise to similar demand for strength and corrosion resistance at -high temperatures;

ice

illustratively the turbine blades employed in such high temperature heavy-duty equipment as jet engines and gas turbines. This industry demand extends to castings, forgings, formed and shaped products, and welded products all in wide variety.

In effort to satisfy industry requirements many proposals have been brought forward, all directed towards the production of metals displaying the requisite qualities of good stress-rupture strength and resistance to creep together with satisfactory ductility under high temperature conditions. Over the years certain ferrous and non-ferrous alloys have been developed which appear to satisfy in part, some of the requirements in narrow fields of application. But even in these instances, the presence of high cost alloying elements in substantial amount has imposed severe economic restrictions, seriously limiting the eld of application. Moreover, the compositions heretofore proposed for commercial utilization have had definite limitation as to the optimum operating temperatures a-t -which they would demonstrate the required mechanical properties.

In many instances the metals of the prior art employed ingredients in the composition which necessitated recourse to vacuum induction melting or vacuum electric arc melting. In some instances the metal of interest was -capable of forging although it was productive of poor castings. Other such metals produced good castings while being relatively incapable of forging. Still other metals displayed poor welding characteristics. Some of the commercially available metals are too hard to be machined, other than by grinding. Poor thermal conductivity characterizes some known metals.

All in all, and for one or more of the several reasons noted, industry has denied full acceptance to the available metals and resignation towards compromise has become evident, with the result of tolerating the observed short life and the inadequate properties of the known metals.

An object of my invention, therefore, is to overcome in large measure the many disadvantages and defects heretofore confronting the industry and at the same time to provide both a metal not Iheretofore known or available, together with various products and articles formed thereof of -widespread application, which new metal essentially comprises a critically proportioned composition of materials economically competitive as to each of first cost, preparation, and subsequent utilization, displaying requisite high strength properties at enduring high temperatures, ranging up to 2200 F. and more; which metal is age-hardenable; and which has widespread application in the form of castings, forgings and welded articles. Referring now more particularly to the practice of my invention I provide an alloy essentially consisting of carbon about 0.20% to 0.40%, chromium about 19.0% to 24.0%, tungsten about 6.0% to 8.0%, cobalt about 9.0% to 10.0%, and remainder principally nickel. Through the inclusion of small additives of certain further essential alloying ingredients, I have found it possible to enjoy the superior high temperature properties of cobalt, while maintaining the amount of this costly component within acceptable range. Accordingly, I further include within the alloy, in approximate percentages by weight, columbium 0.35% to 1.0%, aluminum 0.40% to 1.0%, titanium 0.45% to 0.65%, zirconium 0.20% to 0.60%, and remainder substantially all nickel. Where desired, molybdenum may be optionally included -up to a maximum of 1.0%.

It is to be noted that the various alloying components have in common the characteristic of .being acceptably soluble within the melt, and that they promote optimum strengthening. This attends the generally large atomic mismatch observed with relation to the added' alloying elements and the nickel matrix. The amounts of aluminum and titanium employed are so nicely selected that While the alloy is benefited by their inclusion, nevertheless the usual tendency towards non-metallic inclusions, attributable to the oxygen affinity of aluminum and titanium, is effectively minimized. This possesses the advantage, important from a practical standpoint, that no recourse need be had to vacuum melting practice, nor to the provision of a shielding atmosphere in melting as through the use of inert gases. Quite the contrary, the alloy of my invention may be prepared in the usual electric arc furnace.

Within the broad composition range of my alloy, there may be present manganese from 0.15% to 0.50%, silicon, 0.25% to 0.75%, phosphorus up to .020% maximum, sulphur up to .020% maximum, and iron up to 4.0% maxi* mum.

As to the essential ingredients of my alloy, the chromium inclusion effectively imparts hot strength as well as 'resistance to oxidation, characteristics retained under high temperature conditions. My investigations disclose that nevertheless the chromium content should not depart from range of 19.0% to 24.0%. For while no appreciable tendency of the alloy either to scale or to oxidize is observed under high temperature duty with chromium content Within the limits noted, I find that upon increase in chromium content beyond the upper limit, there apparently is Aformed a eutectic, with high temperature properties tending to decline upon increase in percentage of chromium. With chromium less than the lower limit, inadequate oxidation resistance results.

The ingredients tungsten and cobalt are similarly critical; with less than about 6.0% tungsten, or about 9.0% cobalt the high temperature properties suffer, while with tungsten exceeding about 8.0% or cobalt exceeding about 10.0%. workability suffers and cost of production becomes excessive.

The inclusion of the ingredients columbium, aluminum, titanium and zirconium markedly improves the stressrupture properties. The zirconium additive Within the prescribed amounts also enhances the high temperature ductility and forgeability. I limit the addition of molybdenum to alloys intended for application below 2000 F. The molybdenum contributes to the precipitationhardening phenomenon and to high temperature strength. Manganese and silicon are generally viewed as impurities although the manganese serves to combine with the sulphur impurity. Since the inclusion of these metals lowers the melting point, however, their presence is necessarily limited. For many reasons, the carbon content should be maintained low.

A preferred alloy of optimum properties essentially comprises, in approximate percentages, carbon 0.20% to 0.40% chromium 21.0% to 23.5%, cobalt 9.0% to 10.0%, tungsten 6.75% to 7.75%, molybdenum 0.50% to 1.00%, columbium 0.40% to 0.80%, aluminum 0.45% to 0.90%, titanium 0.45% to 0.65%, zirconium 0.30% to 0.60%, with nickel substantially all of the balance. Within this preferred alloy carbon preferably is about 0.20% to 0.31%, manganese 0.15% to 0.40%, silicon up to 0.60% maximum, phosphorus up to .020% maximum, sulphur up to .020% maximum, and iron 4.0% maximum.

I find the resulting alloy, thus effectively produced through conventional electric furnace practice, is particularly suited for high temperature applications. It effectively withstands temperatures ranging upwards of 2200 F., and this, even in the presence of an oxidizing atmosphere. It can be successfully Worked or processed in many Ways. It can be either cast or forged, as in the production of furnace parts, missile parts, airplane parts, gas turbine parts, and the like. It readily lends itself to welding. It possesses good strength at both room temperatures and at high temperatures, and as well, good stress-rupture properties. It is resistant to scaling at high temperatures, and it is age-hardenable.

4 As specifically illustrative of the alloy of my invention, I give below in Table I the chemical composition of some seven examples. The stress-rupture properties of these seven alloys are given in Table II, and the room temperature mechanical properties of three of them in Table III.

TABLE I Chemical composition of seven' specific alloys of the present invention in percent by weight Heat Numbers Ingredient l .012 20. 1 19.8 21.0 *21.0 23. 9 21. 10 9. 7 9.0 9. 5 *9. 5 9. 5 *10. 0 5. 76 7.10 7. 5 *7. 5 7. 74 *8. 0 Nil 70 63 63 64 75 .36 .40 .50 .49 .31 .90 .43 .49 .50 .30 .51 .95 .50 .57 .50 .49 .47 .59 24 .63 .50 55 50 45 4. 43 3.19 3. 0 *3. 0 3. 22 *3. 0 .0067 0137 Bal. Bal. Bal. Bal. Bal. Bal.

The stress-rupture characteristics obtained from test bars of .252 diameter, machined from sand-cast bars of .75 diameter, solution-annealed for 1/2 hour at 2250" F. and then water-quenched, are given in Table II below. Those specific example lobtained from other than the sand-cast bars are appropriately identified and described.

TABLE II Stress-rupture characteristics of seven alloys 0f Table I 4.0

Approxi- Stress, Rupture mate Temperature Heat No. p.s.i. Time, Percent Hrs. Elong. at Rupture 45 2,200 F 638 2, 350 6.8 52 642 1,890 17. 7 61 638 1, 720 29. 4 55 666 1, 810 34.8 35 660 1,800 36.4 35 642 1, 600 40. 7 42 638 1, 480 79. 3 59 666 430 115. 4 38 643 1, 280 136. 3 42 1 656 1, 780 10. 8 76 1 656 1, 490 22. 6 55 1 656 1, 300 57. 5 34 2 655 2, 100 17.0 9 5 2 655 1, 790 21. 4 10 D 2,100o F 642 4,100 11.5 32 638 3, 415 25. 7 44 638 2, 800 50. 3 54 643 2, 220 112. 8 50 2,000o F 643 6, 33() 12. 4 24 642 5, 385 22. 1 30 638 5,000 36. 8 19 642 4, 790 37. 2 22 638 4, 675 54. 6 19 660 4, 730 64.0 22 642 4, 255 78.8 30 666 3, 850 143. 3 32 638 3, 350 154. 3 37 1 .252 diameter bars removed from longitudinal direction of 1% x 2 forged red. area) stock, solution-annealed M hr. at 2,250 F. and water quenched.

2 .252 diameter bars removed from y, sand-cast plates welded by T.I.G. process using same composition filler rod. Plates solutionannealed hr. at 2,250F. and water quenched after welding.

The room temperature mechanical properties of three of the specific examples set forth in Table I (Heats #656, #643 and #655), one in forged form, another in cast form, and the third cast and then Welded, are given in Table III below:

TABLE III Mechanical properties of Heats #tl-656, #643 and #655 0f Table I, respectively, in forged, cast and welded condition.

SAMPLE 656 FORGED Percent Reduc- Condition Ten. Str., .2% Y.S., Elong tion of p.s.i. p.s.i. (1.4") Area As forged 129, 000 74, 000 29 34 2,250 F. water quenched- 120, 000 54, 750 37 44 2,250 F. water quenched,

aged 8 hrs., 1,700 F 134,000 62, ooo 27 35 SAMPLE 643 CAST Percent Reduc- Condition Ten. Str., .2% Y.S., Elong. tion of p.s.i. p.s.i. (1.4) Area As cast c. 64, 800 38, 000 5. 7 (1) 2,250 F. water quenched. 78, 000 44, 000 14.3 (1) 2,250 F, Water quenched,

aged 8 hrs., 1,700 F 92, 000 56, 000 5. 7 (1) SAMPLE 655 WELDED Percent Reduc- Condition Ten. Str., .2% Y.S., Elong tion of p.s.i. p.s.i. (1.4) Area 2,250 F., water quenched 76, 800 52, 000 8 (1 2) Physical properties determined on cast alloy #643:

Approximate melting range: 2,450-2,500 F.

Density at room temperature: 8.60 guL/co. (.310 lbs/in).

Coefficient of thermal expansion: 75 F.-1,800 F., 8.25X10 1n,/1n./ F.

1 Reduction of area not determined because of heavy orange peel along gage length.

2 Fracture occurred in parent metal.

In conducting the tests reported above I employed a portion of one of the heats to determine the liquidus and solidus of the alloy. The melting range of my new alloy is found to be quite narrow, ranging from 2450 F. to 2500 F. From a practical standpoint I consider this narrow range to be advantageous in foundry practice, since it provides better feeding characteristics, together with less sensitivity to hot-tearing. Density of product was determined for one heat, by measuring and weighing a cylinder machine from one of the cast bars. Observed density of 8.60 gm./cc. was found to be in the same general range as competitive alloys. The same cylinder, thus formed, was heated in a dilatometer furnace, to determine thermal expansion. The observed average coefficient of thermal expansion of 8.29 6 in./in./ F. from room temperature up to 1800 F. was found to be lower than that of most high-temperature, nickelbase allows. This property contributes materially to reduced susceptibility to failure under thermal stressing.

The many room temperature tensile tests reported above were carried out on 0.357 inch diameter tensile specimens machined from the cast or forged material. All machined specimens were X-rayed before testing.

For the forged products, I employed Heat #656 (Table I) cast into a S-inch diameter x 6-inch high ingot mold, with suitable hot top. Following casting, I latheturned the surfaces of ingot, prior to forging. It was then press-forged on a V-die to 31/2" diameter and finished to 1%" x 2" on flat dies, providing about 85% reduction in area. During the forging steps the temperature ranged between 2300o F. down to approximately 1950 F. with reheating at the lower stage. I found tive reheatings suicient to complete the forging operation.

In preparing the specimens for weld tests, I employed metal of Heat #655, and the metal was poured so as to produce a sand-cast plate 8 inches square x 3A inch in thickness. I also rnade several weld rods, sand-cast to 5/16 inch diameter. The plates were X-rayed, solutionannealed, sectioned, and cleaned. I employed a V- grooved weld-joint, at included angle. Welding was accomplished by the T.I.G. process (tungsten electrode with inert gas shielding) with reversed polarity. Employing the cast rod for filler material, I produced a series of 8 Stringer beads along the groove. Following solution-anneal, I examined the welded product metallographically and explored both the room temperature tensile properties and the high temperature stress-rupture life as reported above.

In determining the mechanical properties at room temperature for both the forged and cast products, note that the specimens were tested in three different conditions, the first in the as forged or as cast, the second in the solution-annealed condition (2250 F. followed by water quenching), and the third, following aging for eight hours at 1700 F., after such solution-anneal. For each such condition the specimens were tested as to tensile strength, 0.2% yield strength, percentage elongation and percentage reduction of area. Note that for the welded specimen the test was only in the solution-anneal condition (2250o F. followed by water quenching).

It is to be noted from the test data reported above in Table III that all tensile properties are advantageously high, this being true with regard to the forged, cast, and welded-cast conditions. It is further noted that the highest ductility was obtained in the solution-annealed condition while in general the greatest strengths were produced when the products were age-hardened, following the solution-anneal. Somewhat better tensile properties attend the forged products than the cast specimens, a phenomenon attending the somewhat finer grain size of the forged products.

Upon testing the welded products, it was found that the tensile properties of the weld were quite good as compared to the parent metal. Although the ductility of the weld metal is somewhat lower than that of the parent -metal, this nevertheless is found to be adequate.

As to metallographic examination of the cast products, the as-cast structure was composed of a face-centered cubic matrix which contained a small amount of very line, complex carbides and a third unidentified phase hereafter called alpha phase. The etchant indicated some evidence of segregation. Following solution-anneal I found the micro-structure generally similar to that in the as-cast form, with the interesting exception that most of the very fine, complex carbides had dissolved into the matrix, and that the segregation effect was no longer evident. Finally, with solution-annealing and aging there was developed a very fine, well-dispersed precipitate of complex carbides. I suggest that there was also present a precipitate of Ni3(Al,Ti), although such precipitate usually is too fine for optical examination. I also suggest that the major amount of alpha phase present in all three conditions as a discontinuous grain boundary network, gives rise to a dislocation-pinning mechanism additive to that of the fine complex carbides, thereby enhancing the high temperature strength. The metal of the specimens of both the solution-annealed and aged conditions indicated some evidence of spheroidization and solution of some of the alpha phase in the matrix.

In macrostructure the welded cast alloy demonstrated a typical coarse, columnar, cast structure. The weld metal exhibited a finer grain, probably attributable to rapid cooling. In microstructure the welded cast alloy had excellent joint interface, together with superior fusion bonding. Here the alpha phase was rather fine and was well dispersed in the weld metal. Both the weld and the parent metal contained a very fine substructure.

Microscopic investigation of the forged alloy revealed a fine grain structurein the as-forged condition. The secondary or alpha phase was banded. It was not preferentially Ilocated at the grain boundaries, however, probably :as a result of the hot-working had in forging. Following solution-anneal, the microstructure demonstrated strong evidence of recrystallization. As compared to the 4as-forged condition, the grain structure was coarsened. Annealing twins were present in large number. Upon aging, following solution-anneal, a very line precipitate of complex carbides was noted. Some of these formed preferentially on the annealing twins. This accentuated their appearance. Both those specimens which were solution-annealed and those which were aged following solution-anneal possessed structures demonstrating some evidence of spheroidization, and solution of the alpha phase.

The high stress-rupture values of my alloy substantially retained at 2200 F. are in strong contrast with test data derived from comparative tests upon specimens of the commercially available wrought and cast alloys produced for generally like application. The single gure of the accompanying drawing graphically shows these test results. Since it is generally acknowledged by those skilled in the art that cast alloys generally exhibit better stressrupture properties than their wrought counterparts, data on my alloy in both the cast and wrought forms have been included in the graph.

For the wrought alloys at 1750 p.s.i., it can be seen that a 316 stainless steel of the prior art (about 19% chromium, nickel, 2% molybdenum, :and balance iron) could not sustain the stress. The N155 (about 22% chromium, 20% cobalt, 20% nickel, 3% molybdenum, 2% tungsten, and balance iron) sustained the stress for 3.2 hours while Ren 41 (a Vacuum melted alloy of about 19% chromium, 10% cobalt, 10% molybdenum, 3% titanium, 1.5% aluminum, and balance nickel) sustained the stress for 5.3 hours and Hastelloy X (about 22% chromium, 10% molybdenum, 1% cobalt, 17% iron, and balance nickel) sustained the stress for 8 hours. By comparison my alloy in the wrought form sustained the same stress for l2 hours.

Similarly for the cast alloys it can be seen that at a stress of 1750 p.s.i. the Stel'lite 31 (about 24% chromium, 12% nickel, 6% tungsten, and balance cobalt) sustained the stress for 19 hours (extrapolated). The Na22H alloy (about 28% chromium, 5% tungsten, 48% nickel, and balance iron) sustained the stress for 15.5 hours. The vacuum melted Nicrotung alloy (about 13% chromium, 10% cobalt, 8% tungsten, 4% aluminum, 4% titanium, and balance nickel) broke under stresses of 2800 p.s.i. and 2600 p.s.i. before the'test furnace reached the 2200 F. temperature. By comparison, my alloy in cast form sustained the 1750 p.s.i. stress for 30 hours.

It is apparent from the foregoing that my new nickelbase alloy effectively correlates the three-fold elements of comparatively low rst cost, ease of production, and superior mechanical properties under high temperature conditions. The metal demonstrates practical fulfillment of predicted suitability for welding, forging, and casting, and for machining, drilling, or other fabricating processes. While responding to required toughness and ductility, as suggested above, it can be machined and otherwise iinished without recourse to grinding. Weld strengths closely approach those of the parent metal.

All the foregoing, as Well as many other highly practical advantages, attend the practice of my invention. Thus it will be seen that I provide an alloy in which the various objects hereinbefore set forth, together with many practical advantages, are successfully achieved. The alloy because of the combination of beneficial properties had is particularly suited to the production of annealing furnace parts, turbine blades, missile parts, and other turbine parts.

Since many embodiments of my invention will readily suggest themselves to the workers skilled in the art, I des-ire the foregoing disclosure to be considered as purely illustrative and not as a limitation.

I claim as my invention:

1. A forgeable, weldable, machinable and age-hardenable high-temperature nickel-base alloy having good stress-rupture properties at temperatures -up to 2200 F. and esentially consisting of, in approximate percentages by weight: carbon 0.20% to 0.40%, chromium 19.0% to 24.0%, cobalt 9.0% to 10.0%, tungsten 6.0% to 8.0%, molybdenum up to 1.0%, columbium 0.35% to 1.0%, aluminum 0.40% to 1.0%, titanium 0.45% to 0.65%, zirconium 0.20% to 0.60%, manganese 0.50% max., silicon 0.75% max., phosphorus .020% max., sulphur .020% max., iron 4.0% max., and the remainder substantially all nickel.

2. A forgeable, weldable, machinable, and age-hardenable nickel-base alloy having -good stress-rupture properties at temperatures up to 2200 F. and essentially consisting of, in approximate percentages by weight: carbon 0.20% to 0.31%, chromium 21.0% to 23.5%, cobalt 9.0% to 10.0%, tungsten 6.75% to 7.75%, molybdenum 0.50% -to 1.00%, columbium 0.40% to 0.80%, aluminum 0.45% to 0.90%, titanium 0.45% to 0.65%, zirconium 0.30% to 0.60%, manganese 0.15% to 0.40%, siilcon 0.60% max., phosphorus up to .020% max., sulphur up to .020% max., iron up to 4.0% max., and the remainder substantially all nickel.

3. A forgeable, weldable, machinable and age-hardenable nickel-base alloy possessing superior `high-tempera- Iture stress-rupture properties at temperature up to 2200 F. and essentially consisting of, in approximate percentages by weight: carbon 0.3%, chromium 21%, cobalt 9.5%, tungsten 7.5%, molybdenum 0.6%, columbium 0.5%, aluminum 0.5%, titanium 0.5%, zirconium 0.5%, manganese .15% to .40%, silicon .60% max., phosphorus .020% max., sulphur .020% max., and the balance substantially all nickel.

4. Age-hardenable alloy metal products possessing superior high temperature properties in the age-hardened condition at temperatures up to 2200 F. and essentially consisting of, in approximate percentages by weight: carbon 0.20% to 0.40%, chromium 19.0% to 24.0%, cobalt 9.0% to 10.0%, tungsten 6.0% to 8.0%, columbium 0.35% to 1.0%, aluminum 0.40% to 1.0%, man- -ganese .15% to .40%, silicon .60% max., phosphorus .020% max., sulphur .020% max., titanium 0.45% to 0.65 zirconium 0.20% to 0.60%, molybdenum up to 1.0%, and the remainder substantially all nickel.

5. Annealing furnace parts essentially consisting of, in approximate percentages by weight: chromium 19.0% to 24.0%, cobalt 9.0% to 10.0%, tungsten 6.0% to 8.0%, columbium 0.35% to 1.0%, aluminum 0.40% to 1.0%, titanium 0.45% to 0.65%, zirconium 0.20% to 0.60% and carbon 0.20% to 0.40%, manganese .15% to .40%, silicon .60% max., phosphorus .020% max., sulphur .020% max., with the remainder substantially all nickel.

References Cited by the Examiner UNITED STATES PATENTS 2,432,619 12/47 Franks et al. 75-171 2,460,817 2/49' Fisher 75-171 12,513,468 7/50 Frank-s et al. 75-171 2,513,469 7/50 Franks et al. 75-171 2,540,107 2/51 English et al 75-171 2,840,469 6/58 Gresham et al 754-171 2,920,956 1/60 Nisbet et al 75-171 FOREIGN PATENTS 548,777 11/57 Canada.

DAVID L. RECK, Primary Examiner.

RAY K. WINDHAM, ROGER L. CAMPBELL,

Examiners. 

1. A FORGEABLE, WELDABLE, MACHINABLE AND AGE-HARDEN ABLE HIGH-TEMPERATURE NIDKEL-BASE ALLOY HAVING GOOD STRESS-RUPTURE PROPERTIES AT TEMPERATURE UP TO 2200*F. AND ESSENTIALLY CONSISTING OF, IN APPROXIMATE PERCENTAGES BY WEIGHT: CARBON 0.20% TO 0.40%, CHROMIUM 19.0% TO 24.0%, COBALT 9.0% TO 10.0%, TUNGSTEN 6.0% TO 8.0%, MOLYBDENUM UP TO 1.0, COLUMBIUM 0.35% TO 1.0%, ALUMINUM 0.40% TO 1.0% TITANIUM 0.45% TO 0.65%, ZIRCONIUM 0.20% TO 0.60, MANAGANESE 0.50% MAX., SILICON 0.75% MAX., PHOSPHORUS .020% MAX., SULPHUR .020% MAX., IRON 4.0% MAX., AND THE REMAINDER SUBSTANTIALLY ALL NICKEL. 